// declaring function prototypes
#include <iostream>
using namespace std;

void odd(int a);
void even(int a);

int main()
{
    int i;
    do
    {
        cout << "Type a number (0 to exit): ";
        cin >> i;
        odd(i);
    }
    while (i != 0);
    return 0;
}

void odd(int a)
{
    if ((a % 2) != 0) cout << "Number is odd. \n";
    else even(a);
}

void even(int a)
{
    if ((a % 2) == 0) cout << "Number is even. \n";
    else odd(a);
}